Electro-magnetic rock-drill



(No Model.) 3 Sheets-Sheet 1.

II. N. MARVIN.

ELECTRO MAGNETIC ROCK DRILL.

Patented Jan. I, I8'89.

NIVENTOH,

9N v/Oa TML/4%@ ATTORNEYS N. PETERS. Phwumugmpher. washington. D. C

(No Model.) 3 Sheets- Sheet 2.

H. N. MARVIN.

ELECTRO MAGNETIC ROCK DRILL.

No. 395,575. Patented Jan. l, 1889.

Pff, 14g

W/TNESSES; /NVENTO/?.

N PETERS. Plmm-Lixhegmpher, wminmur D C.

(No Model.) 3 Sheets-Sheet 3.

H. N. MARVIN.

ELECTEC MAGNETIC ECCK DEILL. No. 395.575. Patented JCE. l, 1889.

W/TNESSES.' u /NVENTO/?. I

ATTORNEYS Lil UNITED STATES PATENT HARRY ORTOY MARVIN, OF SYRAFVSE, NEV YGRK.

ELECTRO-MAGNETI ROCKHDRILL..

SPECFICATION forming part of Letters Patent No. 395,575, dated January l, 1889.

Application tiled July 13, 1837. Serial No. 244,150. (No modela .T0 @ZZ whom, it may concern.-

Be itknown that. I, HARRY Ntmron MARvtN, l a citizen ot the l'nited States, and a resident of l Syracuse, in the countyv of Onondaga and State ot' New York, have invented a certain new and use't'ul V.Electro-Magrietic Rock-Drill, ot' which i the following is a speciication.

Mv invention consists in certain improvements in the details ol' construction ot reciplocating tools-such, t'or instance, as roekdrills-in which electro magnetism is employed as the motive power.

The object ol mv invention is more particularly to improve the t'orni ol drill heretofore invented by me, in which l employ a series 1 ot' coils acting Aupon one or more cores and provided with a circular commutator which l is actuated by the cores.

l have herein shown my invention as apt plied to that form ot my drill in which two l reciprocating cores are employed, and some ot' the .improvemcnts hereinafter described are especiall)v amilicable to that torm, while other details ol' improvement would be applii cable to the torni in which a sine-ie core is 1 employed.

The improvements relate to the means for rotating the brushes ol the commutator, to the devices tor turning the drill, to the con Istruction ot' the ii'ommutator and the manner of making connection with the movable por- 1 tion of the same, to the method ot controlling i the torce of the blow or stroke, and to other t minor details, which will be described hereinafter, and then more particularly pointed out 1 in the claims;

In the accompanying drawings, Figure l is a vertical central section of an apparatus emi bodvingl my invention. Fig. is a cross-section ot amagnet-coreand rod passingthrough the same on the line ,X X, l. lf`ig. 53 is a l cross-section on the line Y Y, Fig. l. Fig. -l is a cross-section ot the same core at the point where the splines are applied. Fig. 5 is a cro, section through the upper end ot' the lower core at the point where the ratchetl teeth are formed on said core. Fig. is a vertical section through the portion of the rod where the actuating-pawl that engages with the lower core is located. Fig. 7 is a crosssection at or about the same point. Fig. S is a cross-section of the lower core at the point ot' the eommutator. I a partoll the connect ing; devices between the where the collar 25 engages with the same. Fig. 9 is a plan and section ot' the devices employed tor holding a tool in place at the lower end ol the lower core. Fig. lll illustrates an electric switch employed with the apparatus. Fig. 1l is a plan ot the collar 1) and its retaining-pawl. l) isa top view Fig. lil is a side view of moving core and the commutzuor. Fig. li is a diagram ol. the circuits ot the apparatus. Figs. .15 and lo illustrate llal tripod-sumiort in two of its positions.

ln order that my present invention may be more readilwY understood, l will make reference first to the diagram, Fig. il, where l have shown the coils and cores, and have illustrated diagrammaticallv a connnutator for use in connection with said core and coilsI in a manner heretofore invented b v me.

tf A indicate two cores movable togetherin a series ot' coils. hl, while ll ll', ttc., indicate a series ol' commutator blocks or plates disposed in the l'orm et a c viinder. Une end ot' the series is connected to one end ol' the coils l M, while the other end ot' the series is connected to the other terminal ot the coil series` M. The intermediate blocks or plates, lll, are

connected in regular order to the junctions of the coils )L as indicated. Over the series ot' blocks \\Y ride a pair ot coinmutator-lnushes mounted on arms it, which arms and brushes are respectively in connection with the opposite poles ota galvanie batterv, )il l5, a dlvname-machine, or other source ot electricity. The arms lfl are disposed at such a distance apart as to include in the circuit between them a number ot the coils M, and as the two brushes are moved together over the series of plates the current is shi tted through the coils in regular order, the same number of coils substantiallv being always kept in action in advance ot one or the other of the cores, so as to move the same continuously. The coinmutator-lnushes receive n lotion from the moving cores for this purpose through an;Y snitable mechanical device.

E indicates a stud, block, or arm, moving with the cores by any suitable means and adapted to play between the commutator-arms il. In the position of the parts shown the two upper coils are in circuit, and the core C lOO IO f

will therefore be drawn downward, carrying with it the part E and the commutatorbrushes, through abutment of E upon the right-hand arm. lVhen the core vis brought to rest by the impact of the tool, the momentum of the pa rts will carry the arms li ll farther along over the series of blocks, thus shifting the current downward in the series of coils to a position where an upward attraction will be exerted upon the core A. The cores thereupon begin to rise, moving the columntator in an opposite direction, the block or piece E now engaging' with the left-hand arm ll. lYhen the cores are brought to rest by impact against a suitable stop, the commutator continues its movement by momentum, thus bringing the arms into the position shown in the diagram and shifting the current in the coils to a position for acting downwardly upon the cores C.

Referring` now to the mechanical details of the apparatus` in which my present invention is embodied, the numeral S, Fig. l, indicates a head-piece, between which and a bottom plate, 5, the series of coils numbered t'rom l to 3S, inclusive, are properly secured.

Surrounding the coils is a suitable tube or casing, 5G, for protecting them from dirt and moisture, which tube or casing is preferably air-tight. Between the tube and the coils there is an air-space, as indicated, and at one end of the tube is provided a suitable valve, 50, opening outward, t-he purpose of which is to permit the escape of any air forced in upon the coils at the upper end of the casing.

In the head-plate are one or more openings, ZP, through which air may be delivered upon the coils for the purpose of keeping' them cool. The upper coils, 'l 2 E3 l, of the set are spaced, as indicated, not only from one auother, but from the tube 57, in which the magnetcore for the coils moves. This spacing may be continued downward through the whole series of coils and assists in the circulation of the moving air-current.

Above the casing 5G, and supported by the head-plate, is a. cap, the top of which is indicated at 16. This cap is preferably made airtight, and in its sides are arranged valves A3, adapted to open inward, so as to permit air to enter the space inclosed by the cap. The headfplate 8 also supports an interior tube or cylinder, 9, in which air-openings n are formed for the passage of air.

The lower magnet-core, A, constitutes the drill-rod, and is provided at its lower end with suitable devices for fastening the tool. Above the core A and between it and the core C is a connection of brass, B, or other diamagnetic material, which is entirely free and disconnected from the cores and serves merely to keep them apart.

The magnet or core C is provided with feathers or projections G, which, by entering slots or guideways formed in the brass tube 57, in which theV magnets move, prevent C from rotating. Through 'the core C is bored a longitudinal hole, the upper part of which is somewhat smaller than the lower. The smaller portion has a longitudinal length of two inches or more and is square. It has also a spiral twist or pitch which corresponds to thc twist or pitch ot' a square rod, D, ol brass or other non-magnetic material. The lower part of the hole in the core C is enlarged to the diagonal diameter of the rod D, so that the rod can rotate in the core. This enlarged or clearance hole extends through the brass coupling B and for seme distance into the upper end of the core A, so that the rod D may extend downward to a distance corresponding substantially to the maximum throw of the core.

The rod D is suitably secured to a sleeve, E, which rides in an opening formed in the head l2, closing the upper end of tube t). The sleeve E, whose upper end is extended out into a plate or tlange, as indicated in Figs. l. and l2, carries a projection, E', which is adapted to engage with the arms ll ll at the points Z r of the commutator, as more clearly indicated in Fig. l2. The arms ll are extensions of a plate which surrounds hub E, and which plate rests on a plate, lf3.

The parts being in the position shown, it is obvious that a downward movement of the core C will cause the rod D to rotate, carrying with it the sleeve or plate Eand the projection E', which, by engaging with the connnutator, turns the same. The rod D and the core (l, into which the rod projects, might be made to engage with one another by any other device which would cause the rod D to rotate when the core C moves longitudinally. The upward movement ot' the cere will obviously impart a reverse movement to the projection E.

The construction of the mmnuitator will be described further on.

The drill is rotated iu the following manner: The clearance-hole in the core A, into which the end of rod D passes at the upward end of the stroke, is drifted out into ratchetshaped grooves or teeth, as shown in section in Fig. 5. In the lower end of the rod D is a. mortise-slot, in which is a loose blade, feather,

or pawl, F, the extreme width of which isl somewhat less than the diameter of the rod at that point. This .feather or blade tits the mortise-slot loosely, and is permitted by the pin holding it in place to move outof-.the rod a sufficient distance to engage the ratchetgrooves in A. The feather or pawl F is of steel or other magnetic material, and since on the upward stroke of the drill. the core A is magnetized this magnetism serves to attract the feather or pawl F out-ward and draws it into engagement with the teeth in A, as shown in Fig. 5. ln this mannerthe rod D islocked during a portion of the upward stroke to the rod A, and since the rod D is rotating at this time under the in luence of the magnet (l the rod A then receives motion from .'D, and is rotated to a certain extent. lVhen the motion is reversed, the core or magnet A, being no TOO lIO

, pawl F to slip back into the rod D under influence of the teeth or the ratchet carried or formed in the core A, the edge of the dog' or pawl being' beveled to tit the teeth ot' A, and also being' beveled at its lower side to enable it to easily lind the hole in A. The rod A is locked to prevent its turning in the reverse direction in the following' manner: One or more grooves (indicated at A, Fig. S) are cut in the rod A longitudinally and extending almost its entire length. Embracing' the rod is a collar, S, which is mounted on the block 2, supported by the lower plate, l. This collar carries pins, feathers, or projections T3, lig'. ll, that enter the straight slots in A, so that any rotary motion ot' rod A is sharml by il, while atthe same time long'it udi nal movement of the rod through the collar is not intcn'fered with.

On the outer circumference or any other portion of collar are cut ratchet-teeth, that are engaged by one or more dogs 74. The ratchet and dogs are so arranged as to permit rotation of rod A in the direction in which it l l l l i i x', rig. if.

the electric generator, as indicated in the diagram, and furnish current to the contactwheels. The wheels are pressed into connection with the rings by means of springs L lt will be understood that the contacts l l( represent the extremities of dili'erent wheels mounted on the two arbors, secured, respectively, tothe arms ll. The parts are shown or indicated as in line with one another in 'Fie'. l simply for conveniente The brushes or wheels are pressed against the periphery of the commutatin'-cylintler by means of a spring', The plate carryingA the arms li encircles the hub or plaie li, and the openingI in the platte carrying arms ll is sutiiciently i large to permit the plate to be moved to one side by the springl N, which latter is applied is moved by the ratchet at its upper end.

devices the rod is turned a short distance at or near the completion of each upstroke.

The commutator is constructed as follows:

trundle or lantern wheel and is com `)osed otare suitably held between two blocks or rings of insulating' material, (indicated at 5l and The block 5l rests on a shoulder Vformed on or attached to the cylinder or tube 5), while a end of the cylinder t), presses upon the block 52 and clamps the parts tirmlytogether. The rods lV forni the trundles or spindles ot' the tions of the coils after the manner of the separate insulated conducting' plates or strips of any commutator.

The brushes ot' the ctunmutator consist of wheels V, of copper or other conducting materia-l, which are adapted to mesh with the teeth of the commntator-cylimler. The wheels V are suitably mounted upon arms or spindles l), around the hub ol' plate E. lhe spring' X tends to throw the plate or arms l-i into an eccentric position with reference to the hub and the circumference ol' the etnnmutator, which latter are concentric with each other. '3y so doing it draws the rollers or wheels Y Y firmly against the commutator-bars A screw, Y, passing through the plate il, serves to adj ust the tension of the spring' X.

lt, is obvious that in a drill constructed from a series of coils working` in succession upon a core, as hereinbet'ore described, the influence of any energized set of coils upon either of the The commutator-cylinder is in the form ot a i cores depends upon the relative positions in l which the core and coils are maintained as the a series of conducting' rods or bars, NV, which i l i lt is likewise apparent that the relative position ot' the energized set of coils to the core is I determined bythe position oithebrushes upon i the (iomnnitator,which in turn depends upon screw-nut or washer, l?, applied to the upper l the extent to which the commutator-arins il:

. and the pro'iwftion E may move with relation to one another before comingl into engagement. It, for instance, at the end of the upwheel, and are severally connected to the j uncl stroke of the cores under the influence of the coils acting on core A the arm let, having` stop til, secured to the arms il, and rotate upon said arms 6l as axles.

to be presently described. As they roll around over t-he surface of the cylinder, they make and break connection with the connnutatorrods of the wheel in succession after the manner of an ordinary comn'iutator. The hubs of the wheels are prolonged into contact-heads l K,which bea-r, respectively, upon rings l K, of conducting` material, suitably insulated from one another upon the block 5]. the contact l is longer and smaller than the neck of contact K, as indicated, so that it may bear on ring' l without touching' ring' K. The rings I K are suitably connected with They are held in conj tact with the commutator-cylinder by devices current will be shifted upward in the coils but a short distance, and the downward pull which would be exerted on the core C at the beginning of the next movement downward would not be at its maximum, because the core C would not be sufciently enveloped by the coils in action to permit them to pull to the best advantage. It now the core begin to move downward, the brushes would then be main tained d u ring' such downward movement in such position that the coilsl would remain in advance ot the position of maximum advantage, and consequently the stroke would be of inferior force. Without some means of adjustment in the connections between the i core `and the commutator it is obvious that The neck of the relative position ot' the brushes and coils tothe magnets du ring' upward and downward strokes would be always the same, and the strokes would be of equal force at all times,

which force would be, presumably, the maXi- A IOO IIO

mum force obtainable from the apparatus. lf, however, we cause the con'nnutator at the time of shifting to engage with the part moving with thc core at a point earlier than it otherwise would in .the period of shift, it is obvious that on the beginning ot' the downward movement the brushes will be in advance of the position which they would have it they had been permitted to move farther by their momentum, and that therefore the coils acting on the downward stroke will bein advance ot' the position ot' maximum advantage.

A means that may be employed for securing the adjustment described in the relation of the coils to the core consists of an adjustable block, which is mounted in the head lli, and is in the form ot' a screw having a conical lower end, which is adapted to en with a conical or inclined proj tion, X, proj ecting up from a movable piece, at a point over the center of rotation on the plate E. The piece 22 is a piveted piece pivoted on and carried by the plate E, so as to rotate therewith, and carries a projection, 22', which is adapted to engagewith a pin or projection,'l, on the arm lt of the commutator having the stop Z.

The projection 22 is adapted to perform the function of the projection E at the termination of the upward stroke of the instrument, and normally the pin T would strike the same at the same time that the arm or portion of the commutator caia'ying pin T strikes the projection E. ll'heu the adjustable block or screw i8 vis elevated, the piece X may remain over the center of the plate E and the projection 22 will have no effect. lVhen, however, the screw 1S is lowered, the conical end forces the projection X to one side, thus turning the piece 22 on its pivotor axis and lninging the part 22 in advance of the part E, thus causing projection 2i and )in T to engaee earlier than E would engage l e s c e arm Z', and thus carries the brushes around in a position in advance of the position of maximum advantage andthe force of the blowis diminished. Byturning down the screw 1S more or less the desired force of blow can be obtained. Since in drilling I have deemed it desirable to retract the tool as rapidly as possible at all times, l have shown here an arrangement designed simply yto alter the force of the forward stroke, leaving the backward stroke at all times at a maximum. I do not, however7 limit myself to the application of my invention to altering the force ot' the forward stroke only. lf applied to altering the force of both strokes, the parts would be in normal or maximum position when the projection traveling on the cone of the screw was at a cent al position on the cone or half-way up the incline. Motion of the screw in one direction would affect the forward stroke, Vwhile mot-ion in the other would affect the backward.

By closing up the distance between the stops or points of engagement of arms 14 with projection E', or by splitting` the stop E and causing a central cone to spread the parts, t-he same result would be obtainednamely, to reduce the lost motion between the stop E and arms vll '14.

This part ol' thcinvention consists, broadly, in altering the force ot the stroke in either or both directions by altering the driving connection between the driving-collar E and the ln'ush-plate ll.

l prefer to employ suitable bulling-springs, lV W W7, placed at opposite ends ot' the drill7 as indicated. The springs at the upper end ot the drill are included between the head i2 and a washer, lo, which is adapted. to move with the core (l b v engaging with the splines G on the side of the same. The spring '7 at the bottom of the drill rests upon the head plate or block '-ibetween the same and a washer, 7, with which a should er (indicated at GQ) upon the core A is adapted to engage in ease the core is thrown below its normal limit of movement. The spring ll' is designed to protect the machine from injury in case the point ot' the tool should not meet anyobstruetion.

The spring or springs at the top of the apparatus is preferably made double, and is preferably arranged not only to act as a buffer, but when made sufficiently long and elastic to perform a function as follows: In the ease of a stiff spring, when the magnet system moves upward it does so with considerable velocity, and when the core engages the washer l() the springs VF "5 are compressed to a much greater extent than they would be by a simple pull of the coils upon the lower core, A. Through acquired momentum the brushes are carried around to a distance somewhat farther than they would be carried if the core were moved upward slowly, and by this shifting of the core the position of the coils in action is raised so that they will act upon the upper core. This would he the action if the springs were made quite stiff, so as to check the drill quickly and allow the inertia of the brushes to carry them around. lf, however, the core is brought to rest gradually, the parts of the commutator moving therewith will not necessarily move beyond the point where the core stops, and especially will notdo so if the commutator has considerable friction. lVhen a spring of this kind is employed, it will react and throw the magnet downward, and if the construction of the mechanism be such that the commutator has not shifted to any extent independently of the core at the end of the stroke it is obvious that the brushes will not begin immediately to move with the core C as the latter begins to move downward, because there is considerable lost movement before the part- E or its equivalent would engage with the commutator; hence the shifting of the current in the coils does not begin, although the core C moves, and said core may therefore move down into the iield of the energized coils,

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while at the same time the lower core moves out of the field. It is therefore possible, as will be seen, to make the drill reverse at the upper en d of the stroke without relying upon the inertia of the brushes to carry them around after the magnets come to rest; hence the character of the spring at the top of the drill will affect very materially the action of the apparatus in reversal. It this spring is rig'id and checks the core quickly, the inertia of the commutator will move the position of the eX- citng-coils upward from t-he position where they will act on the lower core to a position i where they will draw downward upon the upper core; but it the spring is flexible the shift brushes meantime remaining stationary. The feature ot a spring adjusted to allow such an action to take place, thus causing reversal without shift of the commutator by inertia, is

not herein claimed, but will be made the subject ot' a separate application.

rlhe current may be turned on and ott' the machine by means ot' a switch, (shown in Fig. 110,) which maybe mounted in any suitable position on the drill.

C2 U" is a copper switch-lever operated by a 3 Block E2 is in l wheel, 23, outside ot the drill. connection with the line-block l) with the drill. The switch is shown in position when current is interrupted. On moving the switch current is gradually admitted to the drill through the resistances.

It is to be observed that t strikes its blocks before C* strikes its own. are thrown in and out .in succession.

separate coils.

Another important teature otl the machine is the utilization ot the magnet-core as the plunger' ot' an air-pump, which maybe employed tor prmlucing circulation ot air about the coils. lfhen the magnet system moves downwartfl and the plunger or magnet A runs out ot the machine on the torward stroke, the internal air capacityot the machine is to that extent increased. 'llu-retore air enters by the valves A" in the outer shell, air gaining acl cess to the interior ot' the brass plunger org dien the piston or magnets return, the same amount of airis forced out ot the machine through l magnet-tube through the holes (i2, te

the valves 5o 50 at the lower part ot the machine.` Thus the magnets act as a pump. The air forced out ot' the plringer-cavity is delivered into the coils through the openings ifi.

The tripod-support olf the drill consists of two bands, (3S ufl, encircling the casing-tube ot' the machine and provided with clamps for clamping them in any desired position. One

band carries two legs, while the upper band g carries but one. These legs are independently adjustable on. their axes. Each legis by inertia will not take place, but the magnet C, through the compressed spring', will bei forced downward into the tield of the coils which last acted upon tbe lower core, the

Thus the tour coils 'lhese i coils may be parts ot the drill-coils or may be independent, and is held lirmly in any desired position by nuts that draw up the shoulders of the leg against the face of the band, the surfaces thus drawn together being properly serrated or notched. Then their clamps are i loosened, the bands may be adjusted both cir- I cumt'erentially and longitudinally and then set in their new adjusted position. The chiel' item in this arrangement is the use of the double band, whereby greater rigidity is obtained, and likewise greater adaptability and l stability, than in the usual forms oi tripod. f lllhat I claim as my invention isl l. In an electro-niagnetic drill, the combil nation, with the reciprocating 1nagnet-core,oi' l the actuating pawl or dog carried thereby, and a magnet for throwing the same into eni gagement with a ratchet connected with the i drill-tool, as and for the purpose described. l 2. The combination, with the magnet A, l provided with ratchet-teeth, ot a pawl of magl netic material mounted, as described, so as to i be capable ot moving into and out of engagel nient by the magnetism of the magnet when l the magnet and pawl come into proximity. l 3. The combination, with the magnet-core A, of a pawl ot magnetic material mounted on l a non-'magnetic support independent ot the core, and a ratchet carried by the core, as and for the purpose described. l. The combination,with the reciprocating l magnet-core, of the rod ot non-magnetic mal terial, whose end is adapted to enter a cavity in the head of the core, and a loose pawl of j magnetic material mounted. on the end of the l rod, and a ratchet connected with the drilltube.

o. ln an electro-magnetic drill or similar tool havin a reciprocating core, magnet-coils spaced as described, to permit circulation ot' air between the coils and guidtstube tor the l reciprocating core. l ti. The combination, withlhe reciprocaling magnet-core, ot a conunutator actuated thereby and having the plane ot its cylindertransl verse to the line ot movement of the core,said cylinder consistin ot a iixed trundle or lantern wheel whose bars or teeth are insulated trom one another, and a ctnnmutator-brushholding arm connected with the reciprocating core and carrying a com'luctiiig-wheel adapted to gear with the lantern-wheel, as and t'or the purpose descrilnird. l T. 'lhe combination` with the c vlimlrical commutator, ot a rotary brush-supporting plate' loosely pivoted on its support' concentrically with the commutator-eylinder, and a spring exm'ting a transverse pressure on said plate, whereby the brushes may be held in contact with the connnutatmliars` as and tor the purpose described. i S. rthe combination,with the reciprocating drill-rod, ot' a reciprocating core or rod, a Q ratchet and pawliior connecting the latter with the drill-rod, and a collar engaging with l the drill-rod provided with a dog or pawl arranged to permit said rod to rotate when con IOO IIO

nected with the reciprocating and rotating rods, but arranged to prevent rotation of the collar in the opposite direction.

9. A combined reciprocating magnet-core and air-pump in which the guide-tube forthe core serves as the cylinder of the pump, in f combination with an air-delivery passage leading from said pump and arranged to deliver a current ot' air upon the magnet-coils, as and for the purpose described.

l0. rThe combination, with the commutato ractuating devices, of the attached rod D and the reciprocating core having a longitudinal hole which receives the rod, said rod and core being connected together by devices, as described, whereby the reciprocatiou ot' the core may impart a rotary movement to the rod.

li. The combination, with the series of coils and the rotary commutator adapted to rotate in a plane parallel to the plane ot' the coils, of the actuating-core and the rod l), extending through or into the core and rotated thereby as said core reciprocates.

The combination, with the magnet-core and a series ot' actuating-coils, of a commutator and connections between the core and.

commutator for impart-ing movement positively to sa-id commutator by the core on its downstroke, said connections being of adjustable length or extent, as and [for the purpose described.

i3. The combination, with a magnet-core and a series of actuating-coils, ot' a commutating device actuated thereby, but movable independently thereof at the end ot' the upthe relation ot' the same with regard to the portion oil the commutator upon which the arm abuts.

l5. The combination, with the two reciprocating cores and their actuating-coils, of a commutator actuated by the core through devices having an adjustable lost motion, whereby the extent of the shift of current in the series ot' coils in an upward direction may be determined, and the consequent torce with which the ripper core is impellcd on the downstroke may be varied.

it). The combination, with the rotary arm 22, adapted to engage with t-he commutator and ad justably mounted on its support, ot' the ad j ustfing-block 1S, engaging' with the arm at or about the center of rotation of the support, as and for the purpose described.

17. The ctnnl'lination, with the drill, of the switch arranged between two sets of resistance-coils, and having its contacts at either side arranged with reference to one another and the two sides of the switch, as described, to throw the coils of each set into circuit singly but alternately with the coils otl the other set.

1S. The combination, with the drill, ot' the two bands, one oi' which carries one adj ustable leg, while the other carries two legs adjustable in del'iendently ot' one another, means for clamping the bands upon the drill, and Y nuts independent of said clamping devices for clamping the shoulders ot` the legs against the Vface oi' the bands, as and t'or the purpose described.

l0. The combination,with the reciprocating magnet-core A, of: a mechanism engaging with said' core for rotating the same on its longitudinal axis, and a simultaneously-reciprocating core, C, connected with said rotating mechanisn|,as and for the purpose described.

20. The bodilymoviug commutator-wheels carrying contacts l K, in combination with the lixed conducting-rings l K.

2l. ln an electro-magnetic reciprocating tool, the combination, with the reciprocating core, of a butter-spring, XV?, the superposed washer, and the shouldered core or dri llholder, as and l'or the purpose (lescribed.

The combination,with the drill, ot a butter spring, W7, consisting of a coiled spring resting upon the lower head-plate and surrounding the drill-rod, said spring being engaged by said rod in case the rod is thrown below its normal limit ot' movement.

Signed at Syracuse,in the county oi' Onondaga and State of New York, this lith day ot' July, A. l). 1887.

'HARRY NOR'ION )[ARYIN.

Witnesses:

W. J. GrLLn'rr, Jas. B. llrreneooi.

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